The present invention relates to a storage system, and mcre particularly to a mass storage system used as a file memory to store documents.
Optical disks of large capacity of data in which users are able to write data of document, so-called direct read after write (DRAW) type optical disks, have recently been put to practical applications. The optical disks have, in addtion to their very large capacity, an advantage that they do not require a large place for storage as compared with magnetic disks. However, the DRAW type optical disks are disadvantageous in that no data can be written in the area on the optical disc where data have already been written. Therefore, the DRAW type optical disks can be used in such a case that data once written need not be updated permanently, but cannot be used in conventional mass storage systems in which data once written need to be changed.